The use of high resolution electron microscopy and image simulation to determine the sharpness of InP/GaInAs interfaces in multiple quantum-well structures

Abstract The structure of interfaces between InP barrier layers and lattice-matched GaInAs quantum-wells in semiconductor superlattice structures has been analysed at the atomic level using high resolution electron microscopy. Images of apparently sharp interfaces have been compared with simulated images of sharp and diffuse interfaces, calculated using the multislice technique, so that an estimation of the sharpness of the interfaces in the experimental images can be made. From comparisons between the simulated and experimental images it appears that at most specimen thicknesses above a minimum value of around 2 nm, it is possible to distinguish between a sharp interface and a diffuse (or mixed) interface, provided that the mixing extends over at least one unit cell (0.587 nm). It is proposed that this technique will allow an upper limit of significant interfacial mixing and/or roughness to be determined relatively rapidly by high resolution electron microscopy for interfaces in InP/GaInAs structures without the repeated need for extensive image calculation.